Re: [PATCH 2/6] KVM: arm64: Remove internal accessor helpers for id regs

Reiji Watanabe
2022-08-30T05:45:31Z

Hi Oliver,

On Wed, Aug 17, 2022 at 2:48 PM Oliver Upton <oliver.upton@linux.dev> wrote:
>
> The internal accessors are only ever called once. Dump out their
> contents in the caller.
>
> No functional change intended.
>
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> ---
> arch/arm64/kvm/sys_regs.c | 46 ++++++++++-----------------------------
> 1 file changed, 12 insertions(+), 34 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e18efb9211f0..26210f3a0b27 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1153,25 +1153,17 @@ static unsigned int raz_visibility(const struct kvm_vcpu *vcpu,
>
> /* cpufeature ID register access trap handlers */
>
> -static bool __access_id_reg(struct kvm_vcpu *vcpu,
> - struct sys_reg_params *p,
> - const struct sys_reg_desc *r,
> - bool raz)
> -{
> - if (p->is_write)
> - return write_to_read_only(vcpu, p, r);
> -
> - p->regval = read_id_reg(vcpu, r, raz);
> - return true;
> -}
> -
> static bool access_id_reg(struct kvm_vcpu *vcpu,
> struct sys_reg_params *p,
> const struct sys_reg_desc *r)
> {
> bool raz = sysreg_visible_as_raz(vcpu, r);
>
> - return __access_id_reg(vcpu, p, r, raz);
> + if (p->is_write)
> + return write_to_read_only(vcpu, p, r);
> +
> + p->regval = read_id_reg(vcpu, r, raz);
> + return true;
> }
>
> /* Visibility overrides for SVE-specific control registers */
> @@ -1226,31 +1218,13 @@ static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
> * are stored, and for set_id_reg() we don't allow the effective value
> * to be changed.
> */
> -static int __get_id_reg(const struct kvm_vcpu *vcpu,
> - const struct sys_reg_desc *rd, u64 *val,
> - bool raz)
> -{
> - *val = read_id_reg(vcpu, rd, raz);
> - return 0;
> -}
> -
> -static int __set_id_reg(const struct kvm_vcpu *vcpu,
> - const struct sys_reg_desc *rd, u64 val,
> - bool raz)
> -{
> - /* This is what we mean by invariant: you can't change it. */
> - if (val != read_id_reg(vcpu, rd, raz))
> - return -EINVAL;
> -
> - return 0;
> -}
> -
> static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> u64 *val)
> {
> bool raz = sysreg_visible_as_raz(vcpu, rd);
>
> - return __get_id_reg(vcpu, rd, val, raz);
> + *val = read_id_reg(vcpu, rd, raz);
> + return 0;
> }
>
> static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> @@ -1258,7 +1232,11 @@ static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
> {
> bool raz = sysreg_visible_as_raz(vcpu, rd);
>
> - return __set_id_reg(vcpu, rd, val, raz);
> + /* This is what we mean by invariant: you can't change it. */
> + if (val != read_id_reg(vcpu, rd, raz))
> + return -EINVAL;
> +
> + return 0;
> }

I see no reason for read_id_reg() to take raz as an argument.
Perhaps having read_id_reg() call sysreg_visible_as_raz() instead
might make those functions even simpler?

Thank you,
Reiji